A photovoltaic solar panel is ordinarily arranged as an array of cells (referred to as a solar array or solar panel) that directly converts solar energy (sunlight) into electrical energy. The electrical energy produced by the solar array can be extracted over time and used in the form of electric power, such as to recharge batteries. Power-Voltage (Power extracted versus Voltage; P-V) characteristics of solar cells are known to exhibit an IV droop characteristics that causes the output power sourced to change nonlinearly with the current drawn. Furthermore, there is a significant variation in the characteristics of the P-V curve for different solar array types.
Solar panels designed for charging a 12v battery or other batteries generate the most power when the output voltage is approximately 17v, this is known as the maximum power point (MPP). However, when a battery is directly connected to the solar panel, the loading due to the battery pulls the solar panel operating voltage down to the battery voltage, which is usually lower than the MPP. By using a DC/DC converter to connect the solar panel to the battery, the solar panel is allowed to run at a higher voltage so that its maximum power output is higher than when the solar panel is connected directly to the battery.
Solar battery chargers are known and some utilize a form of MPP tracker (MPPT) to maximize charging power. Such arrangements generally include a DC-DC power converter that is under control by a digital signal processor (DSP) that controls the duty cycle of the power converter in an attempt to maximize the power delivered to the battery or batteries being charged.